Methods and systems for real-time, in-process measurement of coatings on metal substrates using optical systems

ABSTRACT

A method for measuring the thickness of coatings on metal substrates comprises illuminating a sample comprising a substrate and a coating with light waves of varying wavelengths from a light source, receiving the light waves reflected by the sample at a light collector, diffracting the light waves into a plurality of component wavelengths with a grating, detecting the light intensities of the plurality of component wavelengths at a detector array, generating a reflectance spectral curve using the detected light intensities for each of the plurality of component wavelengths, calculating the thickness of the coating from the reflectance spectral curves of the component wavelengths.

CROSS-REFERENCE TO RELATED APPLICATIONS appples

This application is a continuation of International Patent ApplicationNo. PCT/US18/41541 entitled “METHODS AND SYSTEMS FOR REAL-TIME,IN-PROCESS MEASUREMENT OF COATINGS ON METAL SUBSTRATES USING OPTICALSYSTEMS” filed on Jul. 11, 2018, which claims priority to and benefit ofU.S. Provisional Patent Application No. 62/531,484 entitled “Methods andSystems for Real-Time, In-Process Measurement of Coatings on MetalSubstrates Using Optical Systems” filed Jul. 12, 2017, the entirecontents of which are all hereby incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

The present disclosure generally relates to methods and systems formeasuring the thickness of clear and pigmented coatings applied onvarious metal substrates, more specifically tailored to the products inthe coil coating industry. Embodiments include methods and systems forreal-time, in-process measurement of applied primer and/or top coatcoating thickness, and more particularly methods and systems forreal-time, in-process measurement of coating thickness of a combinationof one or more layers on a static or a moving substrate.

In coil coating industry, most products are made by application of oneor two or more layers of pigmented coatings applied on both sides of ametal coil. These coated products can be used in a wide range ofindustries such as construction, automobile, aerospace, appliances andso on. The coating is applied on a metal substrate at a relatively highspeed of about 500 to 1000 feet per minute. Several alternativetechniques exist to measure the thickness of the coating in an offlineinspection, but there are no non-contact or non-destructive,non-radioactive methods for measuring paint thickness in real-time onthe moving metal substrate during the coating process. The currentwidely used technique for measuring thickness, and thereby controllingquality, is an offline destructive inspection method measuring thecoating thickness of approximately an area of 1 mm² on a coil that hasan area of several thousand square meters. In this method, the thicknessof the coating on the remainder of the coil is simply assumed to besimilar or identical to the measured sample area. The current methodsare time-consuming and provide very little meaningful data for qualityand process control improvements. Other alternate methods include slowand tedious paint weight measurements based on stripping the coatingover a chosen surface area with the difference of weights before andafter the coating is removed providing the weight of the coating over anarea.

The coil coating process generally involves multiple layers of coatingstarting from a pretreatment followed by a primer and top coating. It isimportant to continuously monitor the applied coating accurately as anyunder-application of coating generally results in poor productperformance and the costs of repairing or replacing under-applied coatedcoils are substantial. There are currently no reliable tools toaccurately measure the thickness of these coatings in real-time directlyon the metal coil itself during the coating process. The primer and topcoat layers are usually pigmented and most optical tools are limited tomeasuring transparent or mildly pigmented coatings and even that islimited to offline measurements in most cases. The only alternatemethods for measuring the coating thickness in real-time involveindirect measurements of the paint on the coating applicator rather thandirect measurements of the coated coil itself. At best, the indirectmeasurements of the coating applicator are approximations of thecoatings that may eventually be transferred to the metal coil. Moreover,although there are several optical measurement tools and techniques thatcan measure thickness of transparent or semi-transparent layers, thereare no existing tools or technologies that can directly measure thethickness of a heavily pigmented layers (with a pigmentation level of40% or more) on metal coils of any variety for up to 75 microns.

Thus, there remains a need for methods and systems for direct opticalmeasurement of pigmented coatings on static or moving metal coils inreal-time.

SUMMARY OF THE INVENTION

The present invention relates to measuring and monitoring accuratecoating thickness of heavily pigmented coatings on metal substrates suchas aluminum and steel with pretreatment using the reflectance spectrawhich is obtained using broad spectral range optical system with arraydetector when the coating thickness is between 1 and 75 microns. Themeasured thickness could be a single layer of pigmented coating,multiple pigmented coatings or a combination of transparent andpigmented coatings on metals. The present invention relates tospecifically measuring the primer and top coat thickness in real time atproduction line speeds on one or both sides of the coil simultaneously.

In one embodiment of the present invention, a method for measuring thethickness of coatings on metal substrates may include illuminating asample comprising a substrate and a coating with light waves of varyingwavelengths from a light source. The method may further includereceiving the light waves reflected by the sample at a light collector.The method may further include diffracting the light waves into aplurality of component wavelengths with a grating. The method mayfurther include detecting the light intensities of the plurality ofcomponent wavelengths at a detector array. The method may furtherinclude generating a reflectance spectral curve using the lightintensities for each of the plurality of component wavelengths. Themethod may further include calculating the thickness of the coating fromthe reflectance spectral curves of the component wavelengths.

In another embodiment of the present invention, a system for measuringthe thickness of coatings on metal substrates may include a processorand a light source in communication with the processor, the light sourceconfigured to illuminate a sample comprising a substrate and a coatingwith light waves of varying wavelengths. The system may further includea detection module in communication with the processor. The detectionmodule may include a light collector configured to receive light wavesreflected by the sample, a grating configured to diffract the lightwaves into a plurality of component wavelengths, and a detector arrayconfigured to detect the light intensities of the plurality of componentwavelengths. The system may further include a memory in communicationwith the processor, wherein the memory comprises computer program codeexecutable by the processor. The computer program code may be configuredto generate a reflectance spectral curve using the detected lightintensities for each of the plurality of component wavelengths,calculate the thickness of the coating from the reflectance spectralcurves of the component wavelengths, and display the calculatedthickness of the coating in real-time.

In yet another embodiment, the sample may be continuously moving.

In yet another embodiment, the light waves of varying wavelengths may bebetween about 1000 nm and about 2500 nm.

In yet another embodiment, the light source may be part of a bifurcatedfiber optic cable.

In yet another embodiment, the light collector may be part of abifurcated fiber optic cable.

In yet another embodiment, the grating may match the spectral responseover a specific wavelength range suitable for the sample.

In yet another embodiment, the frequency of the reflectance spectralcurve may be directly proportional to the thickness of the coating.

In yet another embodiment, calculating the thickness of the coating mayoccur in real-time.

In yet another embodiment, a sensor may be configured to detect changesin the distance between the sample and the light source.

In yet another embodiment, illuminating the sample may include varyingthe intensity of the light waves based on the distance between thesample and the light source.

In yet another embodiment, a coating applicator in communication withthe processor may be configured to receive the calculated thickness ofthe coating and adjust the amount of coating applied to the substrate inreal-time.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and characteristics will become moreapparent to those skilled in the art from a study of the followingDetailed Description in conjunction with the appended claims anddrawings, all of which form a part of this specification. While theaccompanying drawings include illustrations of various embodiments, thedrawings are not intended to limit the claimed subject matter.

FIG. 1 is a diagram of a prior art coil coating line.

FIG. 2 is a block diagram of a system for measuring the thickness ofcoatings on metal substrates according to an embodiment of the presentinvention.

FIG. 3 is a diagram of a detection module according to an embodiment ofthe present invention.

FIG. 4 is a flow chart diagram of a method for measuring the thicknessof coatings on metal substrates according to an embodiment of thepresent invention.

FIG. 5 is a graph of the spectral response of a light source accordingto an embodiment of the present invention.

DETAILED DESCRIPTION

The presently disclosed subject matter is presented with sufficientdetails to provide an understanding of one or more particularembodiments of broader inventive subject matters. The descriptionsexpound upon and exemplify particular features of those particularembodiments without limiting the inventive subject matters to theexplicitly described embodiments and features. Considerations in view ofthese descriptions will likely give rise to additional and similarembodiments and features without departing from the scope of thepresently disclosed subject matter.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which the presently disclosed subject matter pertains.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently disclosed subject matter, representative methods, devices, andmaterials are now described.

Following long-standing patent law convention, the terms “a”, “an”, and“the” refer to “one or more” when used in the subject specification,including the claims. Thus, for example reference to “a light source”can include a plurality of such light sources, and so forth.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, conditions, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about”. Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the instant specification and attachedclaims are approximations that can vary depending upon the desiredproperties sought to be obtained by the presently disclosed subjectmatter.

As used herein, the term “about”, when referring to a value or to anamount of mass, weight, time, volume, concentration, and/or percentagecan encompass variations of, in some embodiments +/−20%, in someembodiments, +/−10%, in some embodiments +/−5%, in some embodiments+/−1%, in some embodiments +/−0.5%, and in some embodiments, +/−0.1%,from the specified amount, as such variations are appropriate in thedisclosed products and methods.

Referring now to FIG. 1, a prior art coil coating line 1 is shown. Atypical coil coating line 1 may consist of an entrance accumulator 11that provides a reservoir of uncoiled metal substrate received fromuncoiler 10. The entrance accumulator 11 may be followed bypre-treatment from a cleaning and conversion coating apparatus 12followed by the application of primer coatings from a prime coater 13 onboth sides of the coil. The primer coating is cured in the curing oven14 before a top coat (or finish coat) is applied by the top coater 15 ontop of the primer on both sides of the metal coil. The metal substratewith the coating may then be finished in the finish oven 16 and recoiledby the recoiler 17. All aspects of the coil coating line 1, includingthe speed of the coil substrate and the amount of coating applied, maytypically be controlled with a computer (not shown).

According to some embodiments of the present invention, the systems andmethods of the present invention may be in communication with thecomputer controlling the coil coating line, the computer configured toreceive the calculated thickness of the coating and adjust the amount ofcoating applied to the substrate in real-time. Because the response timeof the measurement of the in-process measurement system in the presentinvention is in milliseconds, there may be a realtime feedback on thethickness of the applied coating. Due to the realtime feedback, theapplication of the coating can be controlled by the coating machine sothat the coating is not only uniform across the width of the coil, butalso is not overapplied, resulting in significant amount of coatingsavings when considering production on an industrial scale. On the otherhand, the present invention may also help eliminate underapplication ofcoating which results in significant savings for coil coatingmanufacturers in reducing scrap and avoiding expensive quality claims.

Referring now to FIG. 2, a system for measuring the thickness ofcoatings on metal substrates according to one embodiment of the presentinvention is shown. The system may include a processor 20 and a lightsource 21 in communication with the processor 20, the light source 21configured to illuminate a sample comprising a substrate and a coatingwith light waves of varying wavelengths. The system may include adetection module 23 in communication with the processor 20 comprising: alight collector 22 configured to receive light waves reflected by thesample, a grating configured to diffract the light waves into aplurality of component wavelengths, and a detector array configured todetect the light intensities of each of the plurality of componentwavelengths. The system may further include a memory 24 in communicationwith the processor 20, wherein the memory 24 comprises computer programcode executable by the processor 20. The computer program code may beconfigured to: generate a reflectance spectral curve using the detectedlight intensities for each of the plurality of component wavelengths,calculate the thickness of the coating from the reflectance spectralcurves of the component wavelengths, and display the calculatedthickness of the coating in real-time.

The processor 20 may receive input signals from and generate instructionsignals for the coil coating applicator controller 26 to process sensorreadings to measure or adjust thickness of coatings in real-time. Theprocessor 20 may also communicate this data to a display 27, allowingoperators to observe the data in real-time. The processor 20 may includeor may be in communication with one or more computer-readable media,such as a memory 24. The processor 20 may further executecomputer-executable program instructions stored in memory 24. Theprocessor 20 may comprise a microprocessor, a digital signal processor(DSP), an application-specific integrated circuit (ASIC), one or morefield programmable gate arrays (FPGAs), or state machines. The processor20 may further comprise a programmable electronic device such as a PLC,a programmable interrupt controller (PIC), a programmable logic device(PLD), a programmable read-only memory (PROM), an electronicallyprogrammable read-only memory (EPROM or EEPROM), or other similardevice.

The memory 24 may comprise a computer-readable media that may storeinstructions, which, when executed by the processor 20, cause it toperform various steps, such as those described herein. Embodiments ofcomputer-readable media may comprise, but are not limited to, andelectronic, optical magnetic, or other storage or transmission devicecapable of providing the processor 20 with computer-readableinstructions. Other examples of media comprise, but are not limited to,a floppy disk, CD-ROM, magnetic disk, memory chip, ROM, RAM, ASIC,configured processor, all optical media, all magnetic tape or othermagnetic media, or any other medium from which a computer processor canread. Also, various other devices may include computer-readable media,such as a router, private or public network, or other transmissiondevice.

According to some embodiments, a bifurcated fiber optic cable 25 may beused for transmitting the light from the light source and also to detectthe light coming back from the light sample. The light source leg of thebifurcated fiber optic cable 25 may consist of 6 illuminating fibers andthe second leg of the bifurcated fiber optic cable 25 may consist of onedetecting fiber. In preferred embodiments, light waves may be providedby a tungsten halogen broadband light source or other suitable broadbandlight source with adequate energy response in the wavelength range ofoperation and the spectral response shown in FIG. 5.

Referring now to FIG. 3, a detection module 30 according to anembodiment of the present invention is shown. The detection module 30may be comprised of several optical components. The detection leg of thefiber optic cable may be attached to an SMA connector 31, followed by afixed entrance slit 32 (which determines the optical resolution of thedetector configuration). The light that passes through the fixedentrance slit 32 may be illuminated on a collimating mirror 33 andreflect from the collimating mirror 33 as a collimated beam towards thegrating 34.

According to some embodiments of the present invention, the grating 34may match the spectral response over a specific wavelength rangesuitable for the sample. The grating 34 may a dispersive opticalcomponent which splits and diffracts light into different wavelengthcomponents. The grating 34 may be carefully chosen to match the sectralresponse over a specific wavelength range that is suitable for differentchemical compositions and paint colors used for coil coating industryaccording to method known in the art. The different light beams from thegrating 34 may then be directed to a focusing mirror 35 and the focusingmirror 35 may focus the first order spectra on the detector array 36.The detector array 36 may have at least 256 elements collecting thereflectance data at 256 discrete wavelengths.

Referring now to FIG. 4, a method for measuring the thickness ofcoatings on metal substrates according to one embodiment of the presentinvention is shown. The method may include at step 40 illuminating asample comprising a substrate and a coating with light waves of varyingwavelengths from a light source. The method may further include at step41 receiving the light waves reflected by the sample at a lightcollector. The method may further include at step 42 diffracting thelight waves into a plurality of component wavelengths with a grating.The method may further include at step 43 detecting the lightintensities of the plurality of component wavelengths at a detectorarray. The method may further include at step 44 generating areflectance spectral curve using detected light intensities for each ofthe plurality of component wavelengths. The method may further includeat step 45 calculating the thickness of the coating from the reflectancespectral curves of the component wavelengths.

According to some embodiments of the present invention, the sample maybe continuously moving. In such embodiments, measuring the coatingthickness in real-time may require consideration of web flutter in thesample metal coil. As the metal coil is coated at high speeds, there maybe a certain amount of web flutter (up and down motion across the widthof the coil). This poses a significant challenge for most optical toolsbecause traditional optical tools use actual values of reflectance tocalculate the thickness of the coating and the up and down motion of thecoil will have such a significant impact on the actual reflectance valuethat it makes the measurements highly unreliable in-process.

According to some embodiments of the present invention, the method mayfurther include at step 46 detecting changes in the distance between thesample and the light source. When either the sample moves too close tothe fiber optic light collector or when the sample goes too far from thefiber optic light collector, the detected light intensities will bebeyond an acceptable range. When such light intensities are detected,the systems according to the present invention can compensate for thechange in distance as described further herein. The system may becalibrated to predefine acceptable ranges of light intensities.

According to some embodiments of the present invention, illuminating thesample may include at step 47 varying the intensity of the light wavesbased on the distance between the sample and the light source. Bycontrolling the intensity of the light in real-time, the effects of webflutter can be mitigated. If the sample moves closer to the sensor thenthe intensity of the incident light may be reduced, and similarly, ifthe sample moves farther away from the sensor, the intensity of theincident light may be increased. After calculating the thickness of thecoating, if it is determined that the distance between the sample andthe light source has changed due to web flutter, the intensity of thelight may be changed before the next measurement is taken.

According to some embodiments of the present invention, the light wavesof varying wavelengths may be between about 1000 nm and about 2500 nm.In preferred embodiments, light waves in this wavelength range may beprovided by a tungsten halogen broadband light source or other suitablelight source with adequate energy response in the wavelength range ofoperation and the spectral response shown in FIG. 5.

A portion of the light waves that are illuminated on the coated samplereflect from the top of the coating and a portion of the light wavespasses through the coating and reflect from the bottom of the top of thesubstrate. The reflectance values may be collected on all the discretewavelengths in a time span of approximately 50 milliseconds or less. Thetwo reflected light waves may be mathematically superimposed to generatea resultant reflectance spectral curve. The spectral curve will take theshape of a periodic waveform. The frequency of the resulting periodicwave may be directly proportional to the thickness of the measuredcoating. The resultant spectral curve will have p- and s-polarizedcomponents of reflectance that generally satisfy the followingequations:

${R_{p} = {{\frac{{n_{1}\cos \; \theta_{t}} - {n_{2}\cos \; \theta_{i}}}{{n_{1}\cos \; \theta_{t}} + {n_{2}\cos \; \theta_{i}}}}^{2} = {{{\frac{{n_{1}\sqrt{1 - \left( {\frac{n_{1}}{n_{2}}\sin \; \theta_{i}} \right)^{2}}} - {n_{2}\cos \; \theta_{i}}}{{n_{1}\sqrt{1 - \left( {\frac{n_{1}}{n_{2}}\sin \; \theta_{i}} \right)^{2}}} + {n_{2}\cos \; \theta_{i}}}}^{2}.R_{s}} = {{\frac{{n_{1}\cos \; \theta_{i}} - {n_{2}\cos \; \theta_{t}}}{{n_{1}\cos \; \theta_{i}} + {n_{2}\cos \; \theta_{t}}}}^{2} = {\frac{{n_{1}\cos \; \theta_{i}} - {n_{2}\sqrt{1 - \left( {\frac{n_{1}}{n_{2}}\sin \; \theta_{i}} \right)^{2}}}}{{n_{1}\cos \; \theta_{i}} + {n_{2}\sqrt{1 - \left( {\frac{n_{1}}{n_{2}}\sin \; \theta_{i}} \right)^{2}}}}}^{2}}}}},$

In the above equations, n₁=complex refractive index of the coating,n₂=complex refractive index of the substrate, θ_(i)=angel of incidence,θ_(t)=transmission angle, R_(p)=p-polarized reflectance component, andR_(s)=s-polarized reflectance component. The p and s polarizedreflectance components are a function of wavelength and have areflectance value at each wavelength.

According to some embodiments of the present invention, the frequency ofthe reflectance spectral curve may be directly proportional to thethickness of the coating.

According to some embodiments of the present invention, calculating thethickness of the coating may occur in real-time. One of ordinary skillin the art will appreciate that the term “real-time” refers to theability to perform measurements and calculate thickness from saidmeasurements with minimal delay—on the order of 100 milliseconds orless.

Illustrative System 1

Since the primer and the top coat are applied sequentially at twodifferent stages on both sides of the coil, a complete overall real-timemeasurement system may consist of the following combination ofindividual inline systems: an in-process measurement system measuringthe front side of the coil where primer is applied, an in-processmeasurement system for measuring back side of the coil where the primeris applied, a third system for measuring the total thickness of theprimer and top coat on the front side of the coil where the top coat isapplied on top of already applied primer, an in-process system formeasuring the total thickness of the primer and the finish coat on theback side of the coil where the back coat is applied on top of alreadyapplied primer.

The measurement systems on the front side of the primer and the top coatmay be linked and communicate with each other, and the thickness of thetop coat can be obtained by dynamically subtracting total thickness ofthe front side of the coil and the primer thickness of the front side ofthe coil.

The measurement systems on the back side of the primer and the back sideof the finish stage may be linked and communicate with each other, andthe thickness of the back coat can be obtained by dynamicallysubtracting total thickness on the back side of the coil and the primerthickness on the back side of the coil.

Illustrative System 2

The present invention performs equally well for measuring wet coatingsin-process with slight modification. Some manufacturers may prefermeasurement of wet coating compared to a dry coating to get feedback onthe amount of applied coating and coating consistency earlier in theprocess before going through the finish oven. The following componentsmay be included in a multi-stage wet measurement system: an in-processmeasurement system measuring the wet coating before it goes into theovern on front side of the coil where primer is applied, an in-processsystem for measuring wet coating before it goes into the overn on theback side of the coil where the primer is applied, an in-process systemfor measuring the total thickness of the primer and wet top coat on thefront side of the coil where the top coat is applied on top of alreadyapplied primer, an in-process system for measuring the total thicknessof the dry primer and the wet finish coat on the back side of the coilwhere the back coat is applied on top of already applied primer.

The dry thickness of the primer may be calculated from the wet thicknessof the primer on both sides of the coil based on the percentage ofsolids by volume in the primer provided by the primer manufacturer.

The measurement systems on the front side of the primer and the top coatmay be linked and communicate with each other, and the thickness of thetop coat can be obtained by dynamically subtracting the calculated dryprimer from the total thickness of the wet top coat and dry primer.Similarly, dry top coat thickness may be calculated from the wetthickness of the top coat based on the percentage of solids by volume inthe top coat provided by the top coat manufacturer.

The measurement systems on the back side of the primer and the back coatmay be linked and communicate with each other, and the thickness of theback coat can be obtained by dynamically subtracting the calculated dryprimer from the total thickness of the wet back coat and dry primer.Similarly, dry back coat thickness may be calculated from the wetthickness of the back coat based on the percentage of solids by volumein the back coat provided by the back coat manufacturer.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

1. A method for measuring the thickness of coatings on metal substratescomprising: illuminating a sample comprising a substrate and a coatingwith light waves of varying wavelengths from a light source; receivingthe light waves reflected by the sample at a light collector;diffracting the light waves into a plurality of component wavelengthswith a grating; detecting the light intensities of the plurality ofcomponent wavelengths at a detector array; generating a reflectancespectral curve using the detected light intensities for each of theplurality of component wavelengths; calculating the thickness of thecoating from the reflectance spectral curves of the componentwavelengths.
 2. The method of claim 1, wherein the sample iscontinuously moving.
 3. The method of claim 1, wherein the light wavesof varying wavelengths are between about 1000 nm and about 2500 nm. 4.The method of claim 1, wherein the light source is part of a bifurcatedfiber optic cable.
 5. The method of claim 1, wherein the light collectoris part of a bifurcated fiber optic cable.
 6. The method of claim 1,wherein the grating matches the spectral response over a specificwavelength range suitable for the sample.
 7. The method of claim 1,wherein the frequency of the reflectance spectral curve is directlyproportional to the thickness of the coating.
 8. The method of claim 1,wherein calculating the thickness of the coating occurs in real-time. 9.The method of claim 1 further comprising detecting changes in thedistance between the sample and the light source.
 10. The method ofclaim 9, wherein illuminating the sample includes varying the intensityof the light waves based on the distance between the sample and thelight source.
 11. The method of claim 1, further comprising adjustingthe amount of coating applied to the substrate in real time based on thecalculated thickness of the coating.
 12. A system for measuring thethickness of coatings on metal substrates comprising: a processor; alight source in communication with the processor, the light sourceconfigured to illuminate a sample comprising a substrate and a coatingwith light waves of varying wavelengths; a detection module incommunication with the processor comprising: a light collectorconfigured to receive light waves reflected by the sample; a gratingconfigured to diffract the light waves into a plurality of componentwavelengths; a detector array configured to detect the light intensitiesof each of the plurality of component wavelengths; a memory incommunication with the processor, wherein the memory comprises computerprogram code executable by the processor configured to: generate areflectance spectral curve using the detected light intensities for eachof the plurality of component wavelengths; calculate the thickness ofthe coating from the reflectance spectral curves of the componentwavelengths; display the calculated thickness of the coating inreal-time.
 13. The system of claim 12, wherein the sample iscontinuously moving.
 14. The system of claim 12, wherein the light wavesof varying wavelengths are between about 1000 nm and about 2500 nm. 15.The system of claim 12, wherein the light source is part of a bifurcatedfiber optic cable.
 16. The system of claim 12, wherein the lightcollector is part of a bifurcated fiber optic cable.
 17. The system ofclaim 12, wherein the grating matches the spectral response over aspecific wavelength range suitable for the sample.
 18. The system ofclaim 12, wherein the frequency of the reflectance spectral curve isdirectly proportional to the thickness of the coating.
 19. The system ofclaim 12, wherein calculating the thickness of the coating occurs inreal-time.
 20. The system of claim 12, wherein the computer program codeis further configured to detect changes in the distance between thesample and the light source.
 21. The system of claim 20, whereinilluminating the sample includes varying the intensity of the lightwaves based on the distance between the sample and the light source. 22.The system of claim 12, further comprising a computer controlling a coilcoating applicator configured to receive the calculated thickness of thecoating and adjust the amount of coating applied to the substrate inreal-time.